There is an increasing need for sterilizable packaging, particularly for medical appliances and supplies, providing an exceedingly high degree of assurance against contamination of the enclosed article. The sterility of heart valves or like prosthetic devices, for example, simply cannot be open to question.
Known receptacles for receiving medical articles and storing those articles in sterilized condition typically comprise a bag of flexible thermoplastic or thermosetting material having an access opening sealed with a membrane that is permeable to sterilizing vapor. Because the closure membrane is secured to the outside surfaces of the bag, large portions of the membrane are exposed to the surrounding environment. Direct impingement on those surface areas of bacteria-carrying dust particles, for example, can lead to contamination of the contents of the package. In addition, storage of the package in a humid atmosphere can lead to the germination of mold spores that can grow through the membrane. The very characteristics that make the membrane usable for a sterilization process render it vulnerable to capillary transfer of moisture across its thickness. Microorganisms can grow on the outside surface of a moist membrane and transfer through to the inside surface even though the membrane pore size may be too small for permeation of airborne bacteria.
Moreover, the removal of a sterile item from known packages often results in contact with a nonsterile edge or other portion of the package, most notably the exterior of the package which is not protected.